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<br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />0728 <br /> <br />APPENDIX B - HYDROLOGY <br /> <br /> <br />INTRODUCTION <br /> <br /> <br />1. Watershed description. - The Purgatoire River basin is located <br /> <br /> <br />in southeastern Colorado and northeastern New Mexico. In areal scope this <br /> <br /> <br />appendix includes only the upper portion of the watershed above the mouth <br /> <br /> <br />of San Francisco Creek (river mile 122) comprising a drainage area of <br /> <br /> <br />1,159 square miles excluding San Francisco Creek. The upper basin lies <br /> <br /> <br />approy.i.mately between longitudes 104010' and 105015', and latitudes 36050' <br /> <br /> <br />and 37020'. C1i~atology and other general hydrologic data presented in <br /> <br /> <br />this appendix pertain more particularly to the basin above Trinidad, <br /> <br /> <br />Colorado, which has a drainage area of 795 square miles. The reach be- <br /> <br /> <br />tween Trinidad dam site and the mouth of San Francisco Creek, 39 river <br /> <br /> <br />miles, is the principal area subject to damage from flood flows .rhich <br /> <br /> <br />originate above the dam site. The portion of the watershed considered <br /> <br /> <br />is shown on plate 1, appendix A. <br /> <br /> <br />2. The Purgatoire River, locally known as Picket Wire River, drains <br /> <br /> <br />the rugged eastern slope of the Culebra Range of the Rocky Mountains. <br /> <br /> <br />East of Trinidad, the river extends across a high plateau. The basin <br /> <br /> <br />width above Trinidad is fairly uniform and averages about 2:) miles. The <br /> <br /> <br />average length of the basin from its headwaters to the mouth of San Fran- <br /> <br /> <br />cisco Creek is 55 miles. North and Middle Forks form the Purgatoire River <br /> <br /> <br />at their confluence, river mile 186. <br /> <br /> <br />3. The largest tribuGary entering the main stem above the Trinidad <br /> <br /> <br />dam site is the South Fork with a drainage area of about 124 square miles. <br /> <br /> <br />This stream drains the southwestern portion of the rugged mountain area <br /> <br /> <br />and enters the main stem at river mile 179. The second largest tributary <br /> <br /> <br />is lDng Carwon which has a drainage area of about 110 square miles. This <br /> <br /> <br />stream enters the main stem at river mile 164 which is within the conserva- <br /> <br /> <br />tion pool of the proposed Trinidad Reservoir. The largest tributary between <br /> <br /> <br />the Trinidad dam site and the mouth of San Francisco Creek is Raton Canyon <br /> <br />1 <br /> <br />APPENDIX B <br /> <br />